Update requests-mock to 1.9.1

[pyup-bot]

This PR updates requests-mock from 1.7.0 to 1.9.1.

Changelog

1.9.1

Bug Fix on 1.9.0 release: 

* Added py.typed file required to make type annotations work.

1.9.0

A number of small improvements: 

* Feature: Adds type hints for python 3. 94 
* Fixes Bug: Handle whitespace encoding in URL. 158 
* Fixes Bug: Allow subclassing the mocker object. 160

1.8.0

Solidifies the behaviour of nested mocking and the real_http variable.

Links

• PyPI: https://pypi.org/project/requests-mock
• Changelog: https://pyup.io/changelogs/requests-mock/
• Docs: https://requests-mock.readthedocs.io/

[pyup-bot]

Closing this in favor of #193